JP6294419B2 - Optical semiconductor device and method of manufacturing optical semiconductor device - Google Patents

Description

  The present invention relates to an optical semiconductor device, and more particularly to an optical semiconductor device having an optical semiconductor element.

  In recent years, semiconductor light-emitting elements such as light-emitting diodes and laser diodes that output blue light have been put into practical use, and development of light-emitting elements that output deep ultraviolet light having a shorter wavelength is being promoted. Since deep ultraviolet light has a high sterilizing ability, semiconductor light-emitting elements capable of outputting deep ultraviolet light have attracted attention as mercury-free light sources for sterilization in medical and food processing sites. In addition, development of semiconductor light emitting devices with higher emission intensity is underway regardless of the output wavelength.

  The light emitting element is accommodated in a package for protecting the element from the external environment. For example, the light emitting element is sealed by bonding a substrate on which the light emitting element is mounted and a lid body disposed on the substrate. The lid is fitted with a translucent window member in the opening of the metal frame, a metal seal ring is provided on the outer periphery of the substrate, and is attached via a brazing material between the metal frame and the seal ring (See, for example, Patent Document 1).

JP 2005-191314 A

  When joining a board | substrate and a cover body through a brazing material, in order to improve bondability, it is desirable to seal, applying a load to a brazing material between a board | substrate and a cover body. At this time, if a part of the brazing material pushed out from between the substrate and the lid flows out toward the mounting surface of the light emitting element, there is a concern that the wiring is short-circuited and the manufacturing yield is lowered.

  The present invention has been made in view of these problems, and one of exemplary purposes thereof is to provide a technique for improving the reliability and manufacturing yield of an optical semiconductor device.

  In order to solve the above-described problems, an optical semiconductor device according to an aspect of the present invention is disposed so as to cover a package substrate having a recess opened on an upper surface, an optical semiconductor element accommodated in the recess, and the opening of the recess. A window member, and a metal joint that seals between the package substrate and the window member. The package substrate has a mounting surface on which a metal electrode on which an optical semiconductor element is mounted is provided, a separation surface provided in a frame shape outside the mounting surface, and a light reflection surface that is inclined from the separation surface toward the upper surface. The metal layer is provided on the light reflecting surface while avoiding the separation surface.

  According to this aspect, by providing the metal layer on the inclined light reflecting surface, the light output to the side of the optical semiconductor element can be reflected by the metal layer and directed to the window member. The light output can be increased. In addition, by providing a separation surface that is not covered with a metal layer between the light reflection surface and the mounting surface, an inclined light reflection surface is connected when the package substrate and the window member are sealed with a metal bonding material. It is possible to stop the flow of the metal bonding material that flows by the separation surface. Thereby, the fall of the yield by a metal bonding material flowing down to a mounting surface can be suppressed.

  The separation surface may be provided at a position one step higher than the mounting surface.

  The metal layer may be provided to avoid a side surface between the mounting surface and the separation surface.

  Further, the metal layer may be provided in a frame shape on the upper surface of the package substrate, and the metal bonding portion may be bonded to the metal layer provided on the upper surface.

  The separation surface may have a width of 100 μm or more.

  The optical semiconductor element may be a light emitting element that emits deep ultraviolet light, and the window member may include a glass plate having a deep ultraviolet light transmittance of 80% or more. The metal layer may include gold (Au), and the metal joint may include gold tin (AuSn).

  Another aspect of the present invention is a method for manufacturing an optical semiconductor device. The method includes a step of accommodating an optical semiconductor element in a concave portion of a package substrate having a concave portion opened on an upper surface, a step of arranging a window member so as to cover the opening of the concave portion, and metal bonding between the package substrate and the window member. Sealing with a material. The package substrate has a mounting surface on which a metal electrode on which an optical semiconductor element is mounted is provided, a separation surface provided in a frame shape outside the mounting surface, and a light reflection surface that is inclined from the separation surface toward the upper surface. The metal layer is provided on the light reflection surface and the upper surface so as to avoid the separation surface, and the step of sealing includes heating the metal bonding material while applying a load between the package substrate and the window member.

  According to this aspect, when the metal bonding material is heated and melted while applying a load between the upper surface of the package substrate and the frame, the flow of the metal bonding material flowing along the inclined light reflecting surface can be stopped by the separation surface. . As a result, a highly reliable sealing structure can be realized by a bonding process in which a load is applied while suppressing a decrease in yield due to the metal bonding material flowing into the mounting.

  ADVANTAGE OF THE INVENTION According to this invention, the reliability of the optical semiconductor device which has an optical semiconductor element can be improved.

It is sectional drawing which shows schematically the light-emitting device which concerns on embodiment. FIG. 2 is a top view schematically showing the light emitting device of FIG. 1. It is a flowchart which shows the manufacturing method of the light-emitting device which concerns on embodiment. It is sectional drawing which shows the manufacturing process of a light-emitting device roughly. It is sectional drawing which shows schematically the light-emitting device which concerns on a modification.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted as appropriate. In order to facilitate understanding of the description, the dimensional ratio of each component in each drawing does not necessarily match the dimensional ratio of the actual device.

  FIG. 1 is a sectional view schematically showing a light emitting device 10 according to the embodiment, and FIG. 2 is a top view schematically showing the light emitting device 10 of FIG. The light emitting device 10 includes a light emitting element 20, a package substrate 30, a window member 40, and a sealing structure 50. The light emitting device 10 is an optical semiconductor device having a light emitting element 20 that is an optical semiconductor element.

  The light emitting element 20 is an LED (Light Emitting Diode) chip configured to emit “deep ultraviolet light” having a center wavelength λ of about 360 nm or less. In order to output deep ultraviolet light having such a wavelength, the light emitting element 20 is made of an aluminum gallium nitride (AlGaN) based semiconductor material having a band gap of about 3.4 eV or more. In this embodiment, particularly, a case where deep ultraviolet light having a center wavelength λ of about 240 nm to 350 nm is emitted is shown.

  The light emitting element 20 includes a semiconductor multilayer structure 22, a light emitting surface 24, a first element electrode 26, and a second element electrode 27.

The semiconductor multilayer structure 22 includes a template layer, an n-type cladding layer, an active layer, a p-type cladding layer, and the like that are stacked on a substrate that becomes the light emitting surface 24. When the light emitting element 20 is configured to output deep ultraviolet light, a sapphire (Al ₂ O ₃ ) substrate is used as a substrate that becomes the light emitting surface 24, and aluminum nitride (AlN) is used as a template layer of the semiconductor multilayer structure 22. Layers are used. The cladding layer and the active layer of the semiconductor multilayer structure 22 are made of an AlGaN-based semiconductor material.

  The first element electrode 26 and the second element electrode 27 are electrodes for supplying carriers to the active layer of the semiconductor multilayer structure 22, and each is an anode electrode or a cathode electrode. The first element electrode 26 and the second element electrode 27 are provided on the side opposite to the light emitting surface 24. The first element electrode 26 is attached to the first inner electrode 36 of the substrate 30, and the second element electrode 27 is attached to the second inner electrode 37 of the substrate 30.

The package substrate 30 is a rectangular member having an upper surface 31 and a lower surface 32. The package substrate 30 is a ceramic substrate containing alumina (Al ₂ O ₃ ), aluminum nitride (AlN), or the like, and is a so-called high temperature fired ceramic multilayer substrate (HTCC, High Temperature Co-fired Ceramic).

  A recess 34 for accommodating the light emitting element 20 is provided on the upper surface 31 of the package substrate 30. The recess 34 is provided with a mounting surface 61, a separation surface 62, and a light reflecting surface 63. The mounting surface 61 is provided at the center of the recess 34, and the first inner electrode 36 and the second inner electrode 37 for attaching the light emitting element 20 are provided. The separation surface 62 is provided so as to surround the outer side or the outer periphery of the mounting surface 61, and is provided at a position higher than the mounting surface 61. The light reflecting surface 63 is provided outside the separation surface 62 and is inclined from the separation surface 62 toward the upper surface 31. A first outer electrode 38 and a second outer electrode 39 for mounting the light emitting device 10 on an external substrate or the like are provided on the lower surface 32 of the package substrate 30.

  The window member 40 is a plate-shaped protection member provided so as to cover the opening of the recess 34. The window member 40 is made of a material that transmits ultraviolet light emitted from the light emitting element 20, and for example, glass, quartz, quartz, sapphire, or the like can be used. The window member 40 is preferably made of a material that has a particularly high transmittance of deep ultraviolet light, high heat resistance, and high airtightness, and is preferably made of a material having a smaller thermal expansion coefficient than the package substrate 30. . It is desirable to use quartz glass for the window member 40 as a material having such characteristics. The ultraviolet light emitted from the light emitting element 20 is output from the outer surface 43 of the window member 40 to the outside of the package through the window member 40.

  The sealing structure 50 includes a first metal layer 51, a second metal layer 52, and a metal joint portion 53.

  The first metal layer 51 is provided in a frame shape on the upper surface 31 of the package substrate 30. The first metal layer 51 has a rectangular frame shape corresponding to the rectangular package substrate 30, and four corners are rounded. The first metal layer 51 is formed, for example, by a metallization process on a ceramic substrate. The first metal layer 51 is formed by plating a base material containing tungsten (W), molybdenum (Mo), or the like with nickel (Ni), gold (Au), or the like. For example, the first metal layer 51 has a laminated structure of W / Ni / Au. Have. The first metal layer 51 is bonded to the metal bonding portion 53.

  The first metal layer 51 is also provided on the light reflecting surface 63 of the package substrate 30. By providing the metal layer on the inclined light reflecting surface 63, the deep ultraviolet light output to the side of the light emitting element 20 can be reflected toward the window member 40 and emitted to the outside of the package. On the other hand, the first metal layer 51 is provided to avoid the separation surface 62. That is, it can be said that the metal layer is not formed on the separation surface 62 and the region where the first metal layer 51 is not formed is the separation surface 62. In addition, the first metal layer 51 is not formed on the side surface 64 located between the mounting surface 61 and the separation surface 62.

  The second metal layer 52 is provided in a frame shape on the inner surface 44 of the window member 40. The second metal layer 52 has a rectangular frame shape corresponding to the rectangular window member 40, and four corners are rounded. The second metal layer 52 is formed by a method such as vacuum deposition or sputtering. The second metal layer 52 is a multilayer film in which titanium (Ti), platinum (Pt), and gold (Au) are sequentially laminated on the inner surface 44 of the window member 40. Note that chromium (Cr) may be used instead of titanium, and copper (Cu) and nickel (Ni) may be used instead of platinum (Pt). The second metal layer 52 is bonded to the metal bonding portion 53.

  The metal joint portion 53 is provided between the first metal layer 51 and the second metal layer 52 and joins and seals between the package substrate 30 and the window member 40 at the outer peripheral portion of the package. The metal joint portion 53 is configured to fill between the first metal layer 51 and the second metal layer 52 and to be located on both sides (both inside and outside the package) sandwiching the second metal layer 52. The metal joint portion 53 is made of a low melting point metal material and includes, for example, an alloy of gold tin (AuSn) or silver tin (AgSn). The metal bonding part 53 spreads between the first metal layer 51 and the second metal layer 52 in a molten state to form a eutectic bond. The metal joint portion 53 is composed of gold tin having a tin (Sn) content of 20% wt to 24% wt so as to have high sealing reliability and a low melting temperature of 300 ° C. or lower. Is preferred.

  The sealing structure 50 is configured such that the entire second metal layer 52 overlaps the first metal layer 51, and the entire second metal layer 52 is positioned in a region where the first metal layer 51 is provided. Has been. That is, the second metal layer 52 is configured not to be positioned on the region where the first metal layer 51 is not provided, and the first metal layer 51 and the second metal layer 52 are not shifted from each other. Specifically, the outer dimensions and inner dimensions of the first metal layer 51 and the second metal layer 52 are adjusted to predetermined sizes as described in detail below.

FIG. 2 schematically shows the dimensions of the package substrate 30 and the window member 40. As illustrated, the outer dimension w ₁₁ of the first metal layer 51 is larger than the outer dimension w ₂₁ of the second metal layer 52, and the inner dimension w ₁₂ of the first metal layer 51 is equal to the second metal layer 52. smaller than the inner dimensions _{w 22} of. Therefore, the width _{w 13} corresponding to the difference between inner dimensions _{w 12} and external dimensions _{w 11} of the first metal layer 51 has a width corresponding to the difference between external dimensions _{w 21} with inner dimensions _{w 22} of the second metal layer 52 greater than w _23. Further, the width w ₁₃ of the first metal layer 51 is configured to be at least twice the width w ₂₃ of the second metal layer 52.

In an embodiment, the outer dimension w ₁₀ of the package substrate 30 is 3.5 mm, the outer dimension w ₁₁ of the first metal layer 51 is 3.2 mm, and the inner dimension w ₁₂ of the first metal layer 51 is 2. 3 mm, and the width w ₁₃ of the first metal layer 51 is 0.45 mm. The outer dimension w ₂₀ of the window member 40 is 3.4 mm, the outer dimension w ₂₁ of the second metal layer 52 is 3.0 mm, and the inner dimension w ₂₂ of the second metal layer 52 is 2.6 mm. The width w ₂₃ of the second metal layer 52 is 0.2 mm. In this embodiment, the inner dimension difference (0.3 mm) between the first metal layer 51 and the second metal layer 52 is larger than the outer dimension difference (0.2 mm) between the first metal layer 51 and the second metal layer 52. .

The separation surface 62 is provided so that the width w ₃ surrounding the outer periphery of the mounting surface 61 is 100 μm or more, and preferably the width w ₃ is 150 μm or more. With the width w ₃ of the separation film 62 to some extent or more, even as the metal bonding material in a molten state is run down toward the upper surface 31 to the light reflecting surface 63, the separation surface 62 of the first metal layer 51 is not provided This prevents the flow and allows the metal bonding material to remain on the separation surface 62.

Next, a method for manufacturing the light emitting device 10 will be described.
FIG. 3 is a flowchart showing a method for manufacturing the light emitting device 10 according to the embodiment. The light emitting element 20 is accommodated in the recess 34 of the package substrate 30 (S10), and the first metal layer 51 and the second metal are aligned by aligning the first metal layer 51 of the package substrate 30 and the second metal layer 52 of the window member 40. A metal bonding material 56 (see FIG. 4 described later) is disposed between the layers 52 (S12). Subsequently, the metal bonding material is heated to a molten state while applying a load between the package substrate 30 and the window member 40 (S14). Thereafter, the metal joint 53 is cooled and solidified while applying a load between the package substrate 30 and the window member 40 (S16).

  FIG. 4 is a cross-sectional view schematically showing a manufacturing process of the light emitting device 10, and shows a process of arranging the metal bonding material 56 and aligning the package substrate 30 and the window member 40. The package substrate 30 and the window member 40 are aligned so that the second metal layer 52 is entirely located on the region of the first metal layer 51. For example, the entire second metal layer 52 can be disposed on the first metal layer 51 by aligning the center positions of the package substrate 30 and the window member 40. In addition, the positioning may be performed so that any of the four corners of the package substrate 30 and any of the four corners of the window member 40 are aligned. In this case, according to the embodiment having the dimensions described above, the center positions of the package substrate 30 and the window member 40 are displaced within a range of ± 50 μm. It can arrange | position so that the whole 2nd metal layer 52 may be located.

  A metal bonding material 56 is disposed between the aligned first metal layer 51 and second metal layer 52. The metal bonding material 56 is a gold-tin preform having a rectangular frame shape corresponding to the second metal layer 52. The metal bonding material 56 has, for example, the same outer dimensions and inner dimensions as those of the second metal layer 52. The metal bonding material 56 may be temporarily fixed to the first metal layer 51 or the second metal layer 52 in advance. The thickness of the metal bonding material 56 is about 10 to 50 μm, preferably about 15 to 30 μm. By sealing using a preform having such a shape and thickness while applying a load 60, the metal joint 53 having a thickness of about 5 to 20 μm can be formed. The load 60 applied at the time of sealing is 50 g or more, preferably 100 g or more, more preferably 200 g or more.

  The metal bonding material 56 is heated and melted while applying a load 60 and spreads between the first metal layer 51 and the second metal layer 52. Since the metal bonding material 56 is pushed out between the package substrate 30 and the window member 40, a part of the metal bonding material 56 may flow down to the inside of the recess 34 along the inclined light reflecting surface 63. However, since the separation surface 62 that is not covered with the metal layer is provided between the light reflection surface 63 and the mounting surface 61, the flow of the bonding material is made to flow on the separation surface 62 using the difference in wettability with respect to the molten metal. Can be fastened. For example, the molten metal stays at the place so as to swell in a ball shape on the separation surface 62 having low wettability.

The step of heating and melting the metal bonding material 56 is preferably performed in an atmosphere of an inert gas such as nitrogen (N ₂ ). As a result, the gold-tin preform in a molten state can be prevented from being oxidized, and the inside of the package can be filled with an inert gas. However, the heating and melting step according to the present embodiment may be performed in an atmosphere of dry air containing oxygen (O ₂ ). By heating and melting the gold-tin preform while applying a load, the metal bonding material 56 can be sealed while preventing oxidation between the first metal layer 51 and the second metal layer 52.

  With the above configuration, according to the present embodiment, it is possible to increase the light extraction efficiency and sealing reliability of the light emitting device 10 and to prevent a decrease in yield in the sealing process. According to one embodiment, gold tin is used as the metal bonding material 56 so that sealing can be performed at a relatively low temperature (about 300 ° C.), and the light reflecting surface 63 is plated with gold. Since gold (Au) is a material having a relatively high reflectivity with respect to deep ultraviolet light, the light extraction efficiency can be further increased by forming the light reflecting surface 63 of gold plating. Further, even if a part of the metal bonding material 56 flows out to the light reflecting surface 63, the main component of the bonding material is gold (Au). Therefore, the influence of the adhesion of the gold tin bonding material on the reflectance of the light reflecting surface 63 is affected. There are few. Therefore, even if the amount of the metal bonding material 56 is increased to increase the sealing reliability and the amount of the bonding material flowing out to the light reflecting surface 63 is increased, the relatively high reflectance of the light reflecting surface 63 can be maintained.

  FIG. 5 is a cross-sectional view schematically showing a light emitting device 110 according to a modification. In the present modification, a first light reflection layer 163 and a second light reflection layer 164 are provided outside the mounting surface 161 of the package substrate 130, and a separation surface is provided between the first light reflection layer 163 and the second light reflection layer 164. The difference from the above-described embodiment is that 162 is provided. That is, in this modification, the first light reflection layer 163 is provided on the outer periphery of the mounting surface 161, and the separation surface 162 is provided on the outer periphery of the first light reflection layer 163. The first light reflection layer 163 and the second light reflection layer 164 are provided with a metal layer, while the separation surface 162 is not provided with a metal layer. Also in this modification, the same effect as the above-mentioned embodiment can be produced.

  The present invention has been described based on the embodiments. It is understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, and various modifications are possible, and such modifications are within the scope of the present invention. It is a place.

  In the above-described embodiment and modification, the case where only the light-emitting element is included in the package of the light-emitting device has been described. In a further modification, an electronic component other than the light emitting element may be incorporated in the package in order to provide an additional function. For example, a Zener diode for protecting the light emitting element from an electrical surge may be incorporated in the housing. Further, a phosphor for converting the wavelength of light output from the light emitting element may be incorporated, or an optical element for controlling the orientation of light emitted from the light emitting element may be incorporated.

  In the above-described embodiments and modifications, the light-emitting device in which the semiconductor light-emitting element is sealed in the package is shown. In a further modification, the above-described sealing structure may be used to seal the light receiving element. For example, the above-described package structure may be used for sealing a light receiving element for receiving deep ultraviolet light. That is, the package may be used for sealing an optical semiconductor element.

  In the above-described embodiment and modification, the configuration in which the metal layer is provided on the outer periphery of the window member and bonded is shown. In a further modification, a metal frame may be provided on the outer periphery of the window member, and metal bonding may be performed between the frame body and the package substrate. The metal frame provided on the outer periphery of the window member may be a material having a thermal expansion coefficient similar to that of the window member, and may be, for example, a Kovar alloy. Gold plating may be applied to the surface of the Kovar metal frame to improve the bondability with the gold-tin alloy.

  DESCRIPTION OF SYMBOLS 10 ... Light-emitting device, 20 ... Light emitting element, 30 ... Package board | substrate, 31 ... Upper surface, 34 ... Recessed part, 40 ... Window member, 53 ... Metal joining part, 56 ... Metal joining material, 60 ... Load, 61 ... Mounting surface, 62 ... separation surface, 63 ... light reflection surface, 64 ... side surface.

Claims (7)

A package substrate having a recess opening on the upper surface;
An optical semiconductor element housed in the recess;
A window member arranged to cover the opening of the recess,
A metal joint for sealing between the package substrate and the window member,
The package substrate includes a mounting surface on which a metal electrode on which the optical semiconductor element is mounted is provided, a separation surface provided in a frame shape outside the mounting surface, and light reflection inclined from the separation surface toward the upper surface. A metal layer is provided from the light reflecting surface to the upper surface avoiding the separation surface,
The metal junction, an optical semiconductor device which is characterized that you bonded to the metal layer provided on the top surface.   The optical semiconductor device according to claim 1, wherein the separation surface is provided at a position one step higher than the mounting surface.   The optical semiconductor device according to claim 2, wherein the metal layer is provided to avoid a side surface between the mounting surface and the separation surface. The optical semiconductor device according to claim 1, wherein the package substrate further includes another light reflecting surface that is inclined from the mounting surface toward the separation surface and provided with a metal layer.   The optical semiconductor device according to claim 1, wherein the separation surface has a width of 100 μm or more. The optical semiconductor element is a light emitting element that emits deep ultraviolet light, and the window member includes a glass plate having a transmittance of the deep ultraviolet light of 80% or more.
The optical semiconductor device according to claim 1, wherein the metal layer includes gold (Au), and the metal joint includes gold tin (AuSn). Accommodating an optical semiconductor element in the recess of the package substrate having a recess opening on the upper surface;
Arranging a window member so as to cover the opening of the recess;
Sealing between the package substrate and the window member with a metal bonding material,
The package substrate includes a mounting surface on which a metal electrode on which the optical semiconductor element is mounted is provided, a separation surface provided in a frame shape outside the mounting surface, and light reflection inclined from the separation surface toward the upper surface. A metal layer is provided from the light reflecting surface to the upper surface avoiding the separation surface,
The step of sealing is seen including the step of heating said metal bonding material while applying a load between the package substrate and the window member,
The method for manufacturing an optical semiconductor device, wherein the metal bonding material is bonded to the metal layer provided on the upper surface .

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